Wireless sensor units are known per se, whereby such sensor units may be used for real-time motion tracking. The sensor unit can have a number of sensor channels. A typical inertial sensor unit generally comprises a plurality of sensors, which data may be read out, for example a sensor unit can contain 3-axis accelerometers, 3-axis gyroscopes, 3-axis magnetometers, a pressure sensor and for internal calibration of the measured sensor values one or more temperature sensors.
The channels may be sampled for reading out data by an analog digital converter (ADC) and processed by the processor. The resulting data is sent to the attached wireless transceiver that sends it to a remote master unit where the data may be used in a suitable real-time application, for example data processing, visualization or control.
Because the sensor data is to be transmitted wirelessly, it is inevitable that some data may be lost in transmission. This is a significant problem for all sensors where the quantity of interest is obtained by further data processing involving solving differential equations using the data measured by the sensor, as is the case for inertial sensors when used to measure motion, i.e. position, velocity and orientation, by integration over time of the measured sensor data. In this case, if data is lost in transmission, the integral value is no longer known and the result must be discarded and the integration process re-initialized introducing errors and unknown constants that significantly negatively affect the accuracy of the motion measurement.